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control radio antenna power to go up via usb

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  • control radio antenna power to go up via usb

    is there a way to control the external antenna from the usb power. i'm totally headless and i want to control the raising and lowering of the antenna from the computer. i was thinking of maybe having a gui button in windows to let me tell the usb cable to give the relay built in the antenna some power to raise it. if you guys know a way, please tell me. thanks.

  • #2
    I'm eventually going to do this with a relay connected to my comm port. Supposedly a simple VB program can be written to control this. My plan was to have it put up the antenna when a label or some control that I can watch for from the outside of the program is visible.

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    • #3
      can you get specific as to what voltage you want to output from the comm ports?


      btw, i love the kmfdm pic

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      • #4
        I don't know what a comm port puts out. I haven't done it yet, but others have. Search for "relay" & "comm port".

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        • #5
          any ideas?

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          • #6
            parallel port has 5v outputs
            2007 Honda Fit Sport 1.5L SOHC-VTEC

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            • #7
              um, yeah, so can you convert it up to 12v? you should be able to, but i don't remember enough from my electronics class to do it.

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              • #8
                um, yeah, so can you convert it up to 12v? you should be able to, but i don't remember enough from my electronics class to do it.

                This post may help you design a relay board, so if you are into it then read on

                First thing first the parallel or com port cannot supply enough current to drive a relay directly. Youll need to use a transistor to boost it up first.

                The problem with connecting directly a relay card to a port is that the BIOS/windows may play with it. Youll see your antenna go up and down before it even boot up to windows. Then some program may even take over it before your application, a printer driver or a hyperterminal perhaps...very unlikley but it can happen.




                If you want it secured then the way to get around it is to assign an ID to the relay board so it only react to a particular software. The software must initialise/send an ID/issue a command to the relay controller before the relay is activated.

                If you dont care about relay comming on/off as the PC boots up then go for the simple design. Not exactly good for controlling the central lock or boot lock for example.

                Otherwise you may need to use a microcontoller or some logic circuitry to ensure the relay only react to a particular application and not to some any software/glitch that put a high or a low signal into the port. You did say you dont know much about electronics but if you know someone who know about MCU programming its not so hard to implement it...a PIC 12C508 can easily intelligently control a bank of relays.

                The PIC can be programmed with a bit-banged UART, set to a particular baudrate, 9600-8-N-1 perhaps. Only the RX/TX lines are needed. The remaining output of the PIC can be multiplexed to control multilple relays.

                A command is sent to a comport...lets say $00-RELAY1-ON

                00 = the ID of the relay board
                RELAY1 = the relay number to be controlled
                ON = turn the relay on

                $00-RELAY1-STATUS
                This return the status of the RELAY1 if its currently ON or OFF


                In event of a power failure the last STATUS of the relay can even be stored in the EEPROM (no EEPROM on 12C508 but many other have)

                Just an example but I think you get the idea.


                Ill be in needing a relay board too but not now so I may look into designing one in the future. I still have the vehicle tracking device to finish off, got abit complicated with voice synthesiser so thats how busy I am. But if you can wait longer Ill publish a decent relay board for all to use. I just need someone to do the window software for me.

                Anyway the idea is there about controlling the relay in a proper way.

                Hope that helps

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                • #9
                  The COM port has two controllable 5V outputs. All you need is a 5V relay. Connect the contacts to the car's 12V and the antenna remote line and the coil to GND and DTR or RTS.

                  EDIT: Damn Ricky, you're too quick!

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                  • #10


                    That was not quick at all, I have to be careful with my spelling...mr spell check is around

                    EDIT :

                    Im not really sure if its safe to directly connect a relay to the port. I know there are some sensitive relays. But a typical car relay have a coil resistance of 80ohms or so. Use a wrong relay and that can damage the port, the back EMF need to be taken into consideration too.

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                    • #11
                      OK, so I'm just slow. I haven't connected relays to a COM port before but to a gamepad and used these (for very small loads!). 500 ohm, and only draw 9mA. That's what I used for my antenna.

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                      • #12
                        NOOOOOO

                        Dont use that...that will burn up in no time.

                        Those type of relay are only used for signals and not to power something. I dont know how much an antenna motor eats up but itll be in something like 2-3A aleast by the look of the size of the motor.


                        The can only handle up to 0.5A of switching. You do need something alot bigger than that. And by the way com port doesnt output +5V. They can swing +- 8V up to 12V or so depending on the comport controller.

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                        • #13
                          Car antennas only use the antenna Power line to switch the antenna.

                          They ahve a sperate power and ground line, like an amp, and use the antenna remote line to send a live signal to switch the motor, not power it.
                          4x4 in a turbo stylee.

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                          • #14
                            Car antennas only use the antenna Power line to switch the antenna.

                            Ahh cheers for the correction mate

                            The motor must have some relay/mechanical switch built in. Just out of interest do you how much current does it require to operate it? The trigger wire still look fairly thick from what I can remember and it is connected to the "hard" on/off/volume control of the radio.

                            I think it was 1980s the last time I saw them, I was a kid then

                            The reed relay just look far too small to me (have used them many times in signals switching applications)...but if it work for "curiosity" reliably then I guess why not follow him

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                            • #15
                              Don't know what sort of power the remote switching used, but I did use the remote line from the headunit to switch a normal 30AMP relay that isolated the Inverter I was using, as well as switching the power antenna.

                              I did manage to burn out one remote line (endedup producing 9V instead of 12V) but as well as the inverter relay, the power antenna was jammed at half way, so it would rumble grumble and grind the motor, then one day the motor stopped working. The same day, the remote line dropped to 9v and wouldn't hold enough juice to operate the relay, but it was a very cheap nasty Pro-Plus headunit.
                              4x4 in a turbo stylee.

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